Breast Cancer is a hormonally dependent cancer, and it has recently been shown that postmenopausal women with elevated serum levels of androgens as well as estrogens are at an increased risk of developing breast cancer. Of particular interest, postmenopausal women with high levels of the adrenal androgens, dehydroepiandrosterone (DHEA) and its sulfate (DHEAS), are approximately twice as likely to develop breast cancer compared to those with lower levels. In the proposed pilot study, we will obtain preliminary data requested by reviewers for a revised R01 application to prospectively determine if increased enzymatic activity at specific step(s) in the steroidogenesis pathway is responsible for increased adrenal androgens in postmenopausal women who develop breast cancer. Specific aims for the proposed pilot study are: 1) quantify the reproducibility of laboratory assays to measure serum pregnenolone, 17OH-pregnenolone, progesterone, 17OH-progesterone, cortisol, and 11-deoxycortisol; and 2) determine if a single measurement of pregnenolone, 17OH-pregnenolone, progesterone, 17OH-progesterone, cortisol, and 11-deoxycortisol adequately reflects longer-term levels. For aim 1, serum aliquots from the same blood draw from 4 women who donate blood to the Fox Chase Biosample Repository will be measured multiple times in multiple assay batches. Coefficients of variation and intraclass correlation coefficients will be calculated to evaluate assay reproducibility. For aim 2, hormones will be measured in serum collected at two different times from 20 women who donated serum to the Columbia, MO Serum Bank. Intraclass correlation coefficients will be calculated to evaluate whether hormone measurements in a single aliquot reflect longer term levels.